My dalliance with FT4

I have had two QSOs on the FT4 mode.

The WSJT-X guide (see sidebar for WSJT-X site) says :-

FT4 is designed for contesting, particularly on the HF bands and 6 meters. Compared with FT8 it is 3.5 dB less sensitive and requires 1.6 times the bandwidth, but it offers the potential for twice the QSO rate.

As I tend to operate at low signal levels on VHF and I never enter contests, this seems to suggest that FT4 is not a mode for me. I have been following the developments but I did not get involved until recently.

However, I see that FT4 is gaining a following on 70cm for the simple reason that the higher QSO rate means that contacts can be completed during short openings in propagation.

On 432MHz modes of propagation such as aircraft scatter often lead to very brief openings but they can produce moderately strong signals. Thus it might make sense to sacrifice some sensitivity to complete a QSO in half the time which otherwise would fail. FT4 might produce a lower signal to noise report but lead to a completed contact.

My first use of FT4 was with Jeremy M0XVF on 70cm at a distance of 133km. For me just a test of the mode on steady tropo. It is amazing to see a QSO completed in just over a minute, rather like a CW contest contact. The procedure is the same as FT8, just that the period is 7.5 seconds and the signals are wider.

My second, and so far final, QSO on FT4 came on 50MHz. Rather than 133km it was 11392km. I was trying to work LU3CQ on FT8 when he announced that he was moving to FT4. I went after him and he worked one station and then me and then was gone. He gave me a report of -18 which was a bit borderline but I was happy to work him for a new country and a new square on 50MHz.

All time FT4 contacts (both of them) at GM4FVM up to 27 May 2023

It took me a week to realise that 11392km is a new distance record for me on 50MHz.

All this just goes to prove that each data mode has its advantages. 

The biggest advantage is to be on the same frequency and the same mode as the station you want to work. This generally helps. It would not have stood me in good stead to have stuck with my previous mode and missed the contact entirely (AM users please note). So I did what I needed to do and switched to FT4.

Largely, different data rates produce a trade off between sensitivity and the period length. So WSPR in standard form has a very slow data rate and so it is very sensitive but it takes a minute to send very little data. In fact it has such a low rate of data that in that minute only beacon information can be sent. You cannot have a QSO on WSPR because the rate is so slow. You can slow WSPR even more - down to sensitivity allowing decodes at -45dB, but it takes 30 minutes to send and everything from the frequency to the propagation has to be very stable.

On HF many people are willing to trade off sensitivity for speed by using FT4. So good is propagation at HF that many operators do not realise that they are giving up 3.5dB in exchange for an early lunch. I cannot really see the point in this in most situations where FT8 would do the job rather better. Maybe this shows that I am a DX-er at heart. More sensitivity and decoding further into the noise is good for me. But at 70cm where propagation can be very brief I suppose that I can see the point of using FT4. 

Anyway, FT4 equals higher data rate, faster QSO, and less sensitivity than FT8. If you cannot hear them you cannot work them, so I prefer FT8 if I can.

As for working my first Argentine station on 6m, well, using FT4 was LU3CQ's idea. I just followed him. I made a deal with the Devil of FT4 and this time it worked. I know that I have to be on the mode that the other station is on or it is not going to turn out well (SSB users please note). 

I do not make the rules, I just follow along like a tender behind (a locomotive).

I need to think about using FT4 at UHF. If it proves to be the right mode then so be it. Maybe giving up some sensitivity is a price worth paying for more contacts. I suspect that Q65 would be better, but then Q65 is better is many situations yet few people use it. Or what about FT9F fast, which seems to be totally forgotten? 

Amateur radio is the art of the possible, and there is no point sticking to impractical modes if they do not meet a need (RTTY users please note). Popular modes like FT8 make lots of things possible, while little used modes might be better in some situations but are not much use if only you are using them.

This "I was only following orders" excuse for switching to FT4 and working Argentina on 6m is hardly good enough.

I need to look back in my excuse list for a better wheeze.

73 Jim

GM4FVM